When I was riding a road bike to work, I used the lower position when I could, but when I was out in traffic I felt better able to keep track of things and was more maneuverable when I as up.

Had a somewhat difficult time answering this without skewing the results. I have aero bars on my bike which I use for the 1/4 to 1/3 of my commute that's on a bikeway. Any time I spend on the aero bars is time I'd likely be in the drops if they weren't there.

I spend a lot of time in the drops and adjust my bars so that I'm comfortable in that position. To me that is where the braking is optimal but I suppose that depends on your hands and where you've got the levers positioned.

IMHO if you're riding on the tops most of the time you've got the wrong bars or they are adjusted wrong. You can't shift from there and on most bikes you can't brake. I wouldn't say the same in regards to hoods.

Not often as its not that comfortable with my back pack and I can't see as well with my take a look mirror. When not commuting I use the drops a lot more.

Pretty much only when there's a serious headwind and I don't need to see that far ahead of me anyway. I could always raise the stem a bit to make the drops more comfortable, but then the hoods and tops would be too high. *shrug*

Yeah can't argue with that. That's exactly why I don't bother messing it all to get more use out of the drops; I'm already happy with where the hoods are, and the tops are close enough for jazz. Two outta three ain't bad.